The X-band Haystack Long Range Imaging Radar (LRIR) is currently undergoing an upgrade that will add a W-Band (92-100 GHZ) imaging capability for satellites in low earth orbits. The upgraded system will be known as the Haystack Ultrawideband Satellite Imaging Radar (HUSIR). The W-band capability will provide a bandwidth of 8 GHz, eight times greater than the previous X-band capability, and is expected to be operational in 2013. The previous X-band capability, which provided an imaging resolution of about 25 cm out to geosynchronous orbit, will be retained and is expected to be back in operation in 2012.

A 1993 paper discussed a potential W-Band upgrade to the Haystack radar.[1] The objective of the proposed upgrade was to achieve a sensitivity comparable to the existing X-Band Haystack LRIR but with a bandwidth of 8 GHz and a resolution of 3 cm. This paper stated the goals for the amplifier of the proposed upgrade were a peak power of 100 kW, an average power of 30 kW, with pulse lengths of between 30 μs and 1.0 ms and a maximum duty cycle of 30%. The proposal required a new antenna, which was estimated to provide a gain of 84 dB. It was estimated that under favorable viewing conditions (normal winter atmosphere with clouds, 60˚ elevation angle, a single 100 μs pulse would provide a sensitivity S = 51.8 dB (1 m2 target, range of 1,000 km). This is very similar to the current sensitivity of the X-band LRIR, suggesting that the W-band radar might also be capable of imaging out to geosynchronous orbit altitudes.[2] However, unlike the X-band radar, the W-band radar was very sensitive to moisture in the atmosphere.

A 2001 Naval Research Laboratory report stated that to meet Space Command requirements, the Air Force had proposed an 8 GHz bandwidth Haystack upgrade that would have a peak power > 5 kW and a duty cycle of 20%.[3] This upgrade was described as enabling the imaging of the “increasing number of orbiting micro-satellites.”

The W-Band Upgrade

There appear to be relatively few technical details about the HUSIR upgrade publicly available. The new W-band capability will operate between 92 and 100 GHz, with a bandwidth of 8 GHz. Although there do not appear to be any official claims about resolution, it has been repeatedly described as providing almost a factor of ten improvement, which would indicate a resolution as low as about 3 centimeters.

The replacement of Haystack’s existing antenna with a new one with the same 36.6 m diameter but with finer tolerances began in 2010.[4] Installation and initial alignment of the new antenna was completed in 2011[5]. The new antenna has a surface tolerance of 100 μm (600 μm in the old antenna) and has higher angular motion speeds of 5 degrees/second in azimuth and 2 degrees/second in elevation (2 degrees and 1.5 degrees per second, respectively for the old antenna).[6]